ISBNnumero

ISBNnumero is a term that appears in some multilingual discussions as a way to refer to the numeric identifier assigned to books under the International Standard Book Number (ISBN) system. It is not an official designation in standard references, but it is used informally to highlight the numeric code that uniquely identifies a book, its edition, and, in some cases, its format.

The ISBN system was created to support cataloging, sales, and inventory control. Since 2007, ISBNs are issued as 13-digit numbers, beginning with 978 or 979. Older 10-digit ISBNs remain valid and can be converted to the 13-digit form by adding the 978 prefix and recalculating the check digit.

The 13-digit ISBN is structured in five parts: a prefix element (978 or 979), a registration group, a registrant (publisher), a publication element, and a final check digit. The check digit is calculated using a modulus 10 algorithm. For example, 978-0-393-04002-9 is a commonly cited valid ISBN demonstrating the 13-digit format.

ISBNnumero is commonly used in libraries, bookstores, publishers, and bibliographic databases. In practice, ISBNs are encoded in barcodes and appear in catalog records, price databases, and metadata feeds. They facilitate precise linking between editions and editions of the same work while avoiding confusion caused by title variants.

Related concepts include the EAN-13 barcode system, which uses the ISBN-13 aligned with the global barcode standard, and the International ISBN Agency, which coordinates national agencies and maintains standards and guidance for publishers.